Heat exchangers the core of which is produced from a three-dimensional hollow laminated panel

ABSTRACT

The Invention relates to an exchanger comprising a network of channels extending between two parallel faces, in order to allow the circulation of a heat transfer fluid in the channels and the heat exchange between this heat transfer fluid and the outside through at least one of the faces. The network of channels is formed by a three-dimensional hollow laminated panel based on fibres hardened by the impregnation of a resin, comprising two two-dimensional woven layers which are impervious and stiff forming the parallel faces, and a stiff weaving of orthogonal fibres, connecting the two layers together by providing a hollow intercalated space by forming rows of parallel walls between them defining the channels.

The invention relates to heat exchangers.

It relates more particularly to exchangers the core of which is producedfrom a three-dimensional hollow laminated panel, obtained from athree-dimensional weaving comprising two parallel layers linked togetherby a weaving of orthogonal fibres defining a hollow intercalated spacebetween the two layers. After resin impregnation and curing, each of thelayers is transformed into a hardened and impervious skin and theorthogonal fibres, also stiffened, keep these two stiff layers at auniform distance. A solar panel produced in this way is for exampledescribed in EP 0 047 443 A2. Another type of exchanger, which can beused as a cooler, is described in DE 199 21 688 A1. DE 91 07 320 U1describes an isothermal container produced with such laminated panels.

These laminated panels have a structural feature based on the fact thatthe orthogonal fibres are not distributed in an isotropic manner overthe entirety of the layers, but in parallel rows: the central hollowspace between the stiff layers is thus divided into a plurality of flowpassages forming parallel channels. The walls defining the channelshowever have a certain porosity in the transversal direction andtherefore between adjacent channels, because of the non-continuousdistribution of the orthogonal fibres along the rows.

As with any heat exchanger, an exchanger produced in this way isconnected to a fluid inlet and to a fluid outlet making it possible toconnect the network of channels to an external circuit, so as tocirculate a heat transfer fluid in the assembly, in order to receiveheat from or transfer heat to the external environment.

A first possibility, disclosed in particular in EP 0 047 443 A2mentioned above, consists of providing inlets/outlets for thesupply/draw-off of fluid which are substantially based at pointsarranged at two diagonally opposite angles of the panel. This techniqueuses the fact that, as explained above, a part of the flow occurs in asubsidiary fashion through the porous walls, leading to a progression ofthe fluid front combining the flows following the two directions,preferred (in the direction of the channels) and subsidiary (through theporous walls).

Such a configuration for the supply/draw-off of fluid is simple toproduce, but it is not always optimal from the point of view of thehomogeneity of the circulation of fluid in the panel. Moreover, theefficiency of the circulation is very dependent on the geometry of thepanel (more or less elongated in one direction or the other) whichtherefore very seriously limits the possibilities of its use.

Another possibility, described for example in DE 199 21 688 A1 mentionedabove, consists of adding “manifolds” or “header tanks” for thedistribution and collection of the fluid at the two ends of the networkof channels for the circulation of the heat transfer fluid, as in thecase of traditional heat exchangers. These manifolds extend over theentire length of the panel and serve on one side for the distribution offluid, on the opposite side for its collection.

The circulation of the fluid is of course much more homogeneous than inthe previous case, as it does not depend on the flow in the transversaldirection between channels, and therefore provides a better heatexchange for the same surface area of panels. It is on the other handmore complex and expensive to implement: the manifolds must be producedseparately, attached and assembled onto the panel, with risks to sealing(bonding defect for example). The presence of the manifolds involvesmoreover an additional space requirement on both sides of the panel,which makes their incorporation more difficult, for example in the formof discrete roof panels, imitating traditional coverings such as slate,corrugated iron, tiles, etc.

One of the purposes of the invention is to resolve all the aboveproblems, by proposing a novel structure for heat exchangers producedfrom laminated panels.

The exchanger is of the general type disclosed by DE 199 21 688 A1mentioned above, i.e. an exchanger comprising a network of channelsextending between two parallel faces, in order to allow the circulationof a heat transfer fluid in the channels and the heat exchange betweenthis heat transfer fluid and the outside through at least one of thefaces. The network of channels is formed by a three-dimensional hollowlaminated panel based on fibres hardened by the impregnation of a resin,comprising two two-dimensional woven layers which are impervious andstiff forming the parallel faces, and a stiff weaving of orthogonalfibres, connecting the two layers together by providing a hollowintercalated space by forming rows of parallel walls between themdefining the channels. Moreover, the exchanger comprises means for thedistribution of fluid, arranged between a fluid inlet and one of theends of each of the channels of the network, and means for collectingfluid, arranged between a fluid outlet and the opposite end of each ofthe channels of the network.

In a manner that characterizes the invention, this exchanger does nothave attached elements forming manifolds for the distribution of fluid,and the means for the distribution, respectively collection, of fluidare means incorporated into the hollow laminated panel, comprising alongitudinal recess produced in the laminated panel along a longitudinaledge of the latter forming an angle with the direction of the channels,this recess (i) opening onto the inner side of the longitudinal edge onthe channels, (ii) being closed on the outer side of this same edge, and(iii) being in fluidic communication with the inlet, respectively outletof fluid.

In a first embodiment, the recess is defined by a gap reserved betweenthe longitudinal edge of the laminated panel and an outer coveringextending over one of the faces of the laminated panel and opening ontothe longitudinal edges of the latter.

In a second embodiment, the recess is formed by removing material in aregion of one of the faces of the laminated panel along the longitudinaledge of the latter, so as to define a U-section groove directedperpendicularly to the plane of the faces and opening onto the face. Theoutlet of the U-section groove can in particular be closed by an outercovering of the panel, extending over the face where the recess isformed.

In a third embodiment, the recess is defined by removing material fromthe sheared edge of the laminated panel along the longitudinal border ofthe latter, so as to define a U-section groove directed parallel to theplane of the faces and opening towards the outside of the sheared edge.The outlet having a U-section groove can in particular be closed by anedging profile arranged along the sheared edge of the laminated panel.

In all cases, the exchanger is advantageously provided with an insertfor guiding fluid and/or creating turbulence, housed in the longitudinalrecess, in particular a twisted tape with a helical configuration.

In a specific application, the laminated panel has a non-rectangularshape of a parallelogram, this panel being arranged vertically with themeans of distribution and collection of fluid inclined with respect tothe horizontal, and with the fluid inlet placed in a low position andthe fluid outlet placed in high position, so as to allow a naturalcirculation of the heat transfer fluid in the exchanger by thethermosiphon effect.

In another application, the exchanger comprises several triangular ortrapezoid panels assembled in roof panels, these panels being arrangedwith the channels oriented in a vertical plane, the recesses formingmeans for the distribution of fluid and the fluid inlet being situatedin the lower part of the panel, and the recesses forming means for thecollection of fluid and the fluid outlet being situated in the upperpart of the panel and along the crests of the roof, so as to allow anatural circulation of the heat transfer fluid in the panels by thethermosiphon effect.

An example of an embodiment of the invention will now be described, withreference to the attached drawings where the same numerical referencesdenote identical or functionally similar elements in all figures.

FIG. 1 is a partial and enlarged perspective view, showing the structureof the laminated panel from which the heat exchanger of the invention isproduced.

FIGS. 2 and 3 are sections through the panel, taken respectively alongII-II and III-III in FIG. 1.

FIG. 4 is a diagrammatic representation illustrating the preferentialand subsidiary directions of flow of the heat transfer fluid in thepanel.

FIGS. 5( a), 5(b) and 5(c) are views of a first embodiment of a heatexchanger according to the invention produced from a panel such as thatin FIG. 1, this exchanger being shown respectively in plan view, inexploded cross-section before moulding, and in cross-section in itsfinal configuration.

FIGS. 6( a), 6(b) and 6(c) are similar to the previous ones for a secondembodiment of the invention, respectively in plan view, in explodedcross-section before moulding and after machining of the laminatedpanel, and in cross-section in its final configuration.

FIGS. 7( a), 7(b 1), 7(b 2) and 7(c) are similar to the previous onesfor a third embodiment, respectively in plan view, in cross-sectionbefore machining, in exploded cross-section after machining and beforeinstalling the border profiles, and in cross-section in its finalconfiguration.

FIGS. 8( a), 8(b) and 8(c) are similar to FIGS. 5( a), 5(b) and 5(c),for an embodiment variant with optimization of the flow of the fluid inthe collection and distribution recesses.

FIG. 9 is a diagrammatic example of an exchanger according to theinvention applied to the production of a solar panel for producing hotwater, with natural circulation by the thermosiphon effect.

FIG. 10 is a view of the roof of a garden shed, comprising solar panelsaccording to the invention for producing hot water, for example forheating a swimming pool.

FIG. 11 is a cross-section view of the detail referenced as XI-XI inFIG. 10, showing the structure of the roof taken at the level of the hipof the roof.

FIGS. 1 to 3 illustrate the structure of the three-dimensional hollowlaminated panel with which the heat exchanger is produced according tothe present invention.

This laminated panel is obtained from a three-dimensional weavingcomprising two parallel layers 10, 12 linked together by a weaving oforthogonal fibres 14 so as to define between these two layers a hollowintercalated space 16.

The product is initially presented in the form of rolls of fabric, whichcan be cut and shaped to the desired dimensions and configuration. Thefibres, generally glass fibres, are then impregnated with a resin(polyester, epoxide, phenolic, etc.) which after curing transforms eachof the layers into a hard and impervious skin. The orthogonal fibres,also stiffened, keep these two stiff layers at a uniform distance,externally in the form of a stiff and hollow laminated panel having twoparallel faces.

The product is commercially available under the name Parabeam 3D GlassFabrics from the company Parabeam Industrie-Handelsonderneming B.V.,Helmond, Netherlands. Different thicknesses are available from 3 to 22mm, and the final product obtained has excellent properties in terms oflightness, compressive strength and shear, as well as a low thermalresistance.

This product also has a structural feature based on the fact that theorthogonal fibres 14 are not distributed in an isotropic fashion overthe entirety of the layers, but in parallel rows. The weaving of theorthogonal fibres is sufficiently tight along these rows so that thelatter define the parallel walls 20 dividing the central hollow space 16into a plurality of flow passages or parallel channels 18. It should benoted that the orthogonal threads are distributed along these rows in adiscontinuous fashion, which results in a certain amount of porosity ofthe walls 20 in the transversal direction, i.e. between two adjacentflow passages 18.

This panel can be used as a heat exchanger by circulating a heattransfer fluid in the hollow intercalated space. This circulation isshown diagrammatically in FIG. 4: the circulation preferentially takingplace along channels 18 defined between the parallel walls 20corresponding to the rows of orthogonal fibres (arrows 22). Taking intoaccount the porosity of these walls 20, the flow also takes place, in asubsidiary fashion, through these porous walls (arrows 24), in a ratiotypically of the order of 90%/10%. The result is fluid progressionmainly along the channels 18, but also partially in a directionperpendicular to these channels.

FIGS. 5( a), 5(b), 5(c), illustrate a first embodiment of the invention.

The invention resides in the way in which the heat transfer fluidarriving via an inlet 26 and leaving via an outlet 28 is distributedwithin the panel 30.

This embodiment utilizes a mould 32, the width of which is slightlygreater than that of the panel 30, the difference being for example ofthe order of 10 to 20 mm with respect to the overall width of the panel(for a typical width of panel of 0.60 m). The panel 30, the dimensionsof which can for example reach 4.50×0.60 m, is sandwiched between anouter skin 34, in particular a black outer skin for a face which will beexposed to solar radiation in the case of a solar collector, and aninner skin 36. The assembly formed by the laminated panel 30 and theinner and outer skins 36, 34 is placed in the mould 32, in theconfiguration illustrated in exploded view in FIG. 5( b). Once theassembly is moulded, the latter has the configuration in FIGS. 5( a) and5(c), with in particular, on both sides of the panel 30 in the widthdimension, a gap 38 provided between the longitudinal edge of the end ofthe panel and the edge (the outer skin) of the actual heat exchanger 40.Taking into account the differences in width indicated above, this gaphas a width of the order of 5 to 10 mm, and it opens out, on the innerside, onto one of the ends of each of the channels 18 of the laminatedpanel, the latter having been orientated so that its channels,corresponding to the main direction of flow of the fluid, form an anglewith the edge along which the gap 38 extends, a right angle in theexample illustrated (i.e. the channels extend and open outperpendicularly to the direction in which the gap 38 extends). On theouter side, the gap 38 is closed in a sealed fashion by the wall of theouter skin 34.

The two gaps 38 thus defined are connected, one to a fluid inlet 42, theother to a fluid outlet 44, this inlet and outlet being preferablydiagonally opposite in order to allow a flow of fluid in the panel 30that is as homogeneous as possible.

For a panel 40 used as a solar collector, the panel is mounted with thecold water feed 26 in the lower part and the hot water draw-off 28 inthe upper part, so as to allow the hot water to rise by naturalconvection in the panel mounted vertically (or inclined, with the sideof the outlet 28 at the top).

The inlet and outlet 42 and 44 can be produced by simple drilling,equipped with a connection to a pipe, respectively for the supply ordraw-off of fluid.

FIGS. 6( a), 6(b), 6(c), illustrate a second embodiment of theinvention.

In this embodiment, the configuration of the different elements iscomparable, but the gaps 38 which serve for the distribution andcollection of the fluid are produced not by blocking-out a gap at thetime of moulding, but by machining the panel 30, as can be seen inparticular in the exploded view in FIG. 6( b). The panel is machinedafter polymerisation, for example by forming therein a U-section grooveperpendicularly to the plane of the faces using a router, this groovebeing a non-penetrating groove opening onto the face of the panel 30 andextending over the entire length of the longitudinal edge of the latter.Here also, the fluid inlet and fluid outlet 42, 44 are placed at theends of the groove 38, in diagonally opposite positions on the panel 30.

FIGS. 7( a), 7(b 1), 7(b 2) and 7(c) illustrate a third embodiment ofthe invention.

In this embodiment, the recesses 38 are also formed by machining, butthis machining is not carried out by the removal of material from one ofthe faces of the panel, but by the removal of material directly from thesheared edge, over a width slightly less than the total thickness of thepanel, so as to leave the two existing parallel faces 10, 12, theremoval of material being carried out only in the region of theorthogonal fibres situated between these two parallel faces. In this waya U-section groove is obtained, directed parallel to the plane of thefaces and opening towards the outside of the sheared edge of the panel30. The imperviousness of this groove is obtained on the outer side by asimple border profile 46 attached along the sheared edge of thelaminated panel, optionally on the four sides of the panel 30 so as toform a stiff frame for holding and protecting this panel.

FIGS. 8( a), 8(b) and 8(c) illustrate a variant of the first embodimentin FIGS. 5( a), 5(b) and 5(c). This variant, which is moreoverapplicable to the other embodiments described, consists of placing inthe gap or recess 38 a spiral wrap, for example having the shape of atwisted tape in a helical configuration, the function of which is toguide and distribute the fluid along the recess or gap 38, and to createturbulences at this location capable of improving the heat exchange andthe distribution/collection of the fluid entering/leaving the parallelchannels of the panel 30.

It is possible to combine or modify several single collectors such asthose that have just been described, for example by placing them inseries or in parallel, superposition and/or juxtaposition of collectorswith several passes in cross flow or counterflow, partial paths inopposite directions, etc., according to techniques which are known perse.

Moreover, although a collector has been described which is produced froma flat panel, this shape is in no way limitative, and the techniqueimplemented makes it possible to very easily obtain very varied shapes:a panel that is curved, corrugated, etc.

In general, the heat exchanger that has just been described is suitablefor a very large number of other applications, among which there can bementioned in a non limitative fashion:

-   -   solar collector panels: taking account in particular of the        multiplicity of shapes and appearance which can be produced, it        will be easy to integrate the panel with the surroundings. It is        even quite possible to produce an entire roof following the        technique according to the invention, the panel then acts both        as roof covering and solar collector. These collector panels can        be used in all the applications generally assigned to solar        panels: producing domestic hot water, heating water for swimming        pools, atmospheric scavenging for heat pumps, etc.    -   use as a keel cooler for cooling boat engines (the heat transfer        fluid being the water for cooling the engine, and the exchanger        being mounted below the waterline). It should be noted in        particular that in this application the panel can form an        integral part of the hull of the boat, which avoids the        drawbacks of an attached element, and that its glass fibre/resin        composition presents no risk of corrosion or electrolysis, even        in a marine or polluted medium.    -   cool box, with of ethylene glycol flowing in a closed circuit        within the walls of the box, instead of an evaporator or a        eutectic plate placed in the refrigerated compartment.    -   heating wall, which can be used in a wide variety of        applications: made-to-measure radiator, heated cupboards, etc.        For example, in a bathroom a mirror can be mounted on a panel        according to the invention, the hot water used for example for        the shower flowing in this panel, which avoids any condensation        on the mirror, even in a very damp environment (inside the        shower cabinet).

FIG. 9 illustrates a particular implementation of the invention, inwhich the heat exchanger is used as a solar panel for the production ofhot water. The heat exchanger 40 can be produced according to any one ofthe embodiments disclosed above.

Very advantageously, the panel 30 does not have a rectangular shape, asin the examples disclosed above, but a parallelogram shape, the panelbeing placed vertically and produced so that the parallel channels, andtherefore the main direction of flow of the fluid, extends vertically.The gaps or recesses 38 for the collection and distribution of the fluidare then, due to the parallelogram shape, inclined with respect to thehorizontal, the fluid inlet 42 is placed in a low position in the recessor inclined lower gap, and the fluid outlet 44 in a high position of therecess or inclined upper gap. In fact, this configuration will have atendency to promote a natural circulation of the heat transfer fluid inthe exchanger by natural convection and the thermosiphon effect, withoutthe need to provide additional means of pumping. It will then besufficient to connect the hot water outlet pipe 28 and the cold waterinlet pipe 26 to an appropriate exchanger 50 such as a domestic hotwater tank or a heat exchanger for the water of a swimming pool in orderto obtain a simple, effective and inexpensive heating device.

The heat exchanger 40 thus produced can be for example incorporated inan enclosure element 52 or similar, so as integrate it invisibly intothe domestic environment, by giving the visible face of the laminatedpanel a material effect (imitation wood, etc.) and by adding to itattached pieces 54, 56 making it possible to conceal the parallelogramshape of the actual heat exchanger, and to give the assembly a shapesimilar to that of an enclosure panel or similar.

FIGS. 10 and 11 illustrate another embodiment implementing the exchangerof the invention, in which roof panels of a garden shed are used assolar panels to heat water, in particular the water for a swimming poolor a jacuzzi, without the need for an external power supply or a complexsystem of distribution and pumping.

The roof has the general shape of a pyramid, produced from heatexchangers 40 produced for example in accordance with the embodiment inFIG. 5 disclosed above. The laminated panels 30, which each constitute aheat exchanger 40, have a general trapezoid shape. A recess 38 is formedon the lower side of the trapezium (one of the two parallel sides), andit is provided with fluid inlet apertures 42 connected to respectivecold water feed pipes 26. The recess 38 thus configured forms acollector at this location for the distribution of cold water in all ofthe parallel channels of panel 30.

The upper side of the trapezium and its lateral sides (the inclinedsides) are also provided with a recess 38, which acts as a collector forthe fluid that is heated as it passes through the panel 30. The recess38 formed on the upper side of the trapezium is provided with apertures44 in fluidic communication with a hot water outlet pipe 28.

As can be seen in FIG. 11, the trapezoidal panels 30 forming each of theslopes of the roof are assembled so as to form the frustum of a pyramid.These panels are assembled together for example by fixing theirperipheral region (where the outer skin 34 and the inner skin 36 arewelded, forming a flattened peripheral rim) onto a batten 58 acting as ahip rafter, for example using a screw 60 passing through the peripheralrim 62. A bonded angle piece 64 ensures the external finishing and hidesthe screw heads 60 and the peripheral edge 62.

The assembly thus constituted is completed by a pyramidal ridge element66 defining a cavity 68 in communication with the apertures 44, for therecovery and collection of the hot water after the latter has passedthrough the channels of the different panels forming the heat exchangersfrom bottom to top, by natural convection.

This roof structure can be produced very simply, essentially by bondingand by screwing, therefore at low cost. Moreover, the use of thelaminated panels makes this structure extremely light, and it can besimply installed on support pillars 70, without the need to providereinforcement or additional carpentry items.

Moreover, it is extremely easy to give the visible face a materialeffect (imitation tiles or slates) so that it can be discretelyintegrated with the surrounding landscape.

1. A heat exchanger, comprising: a network of channels (18) extendingbetween two parallel faces (10, 12), in order to allow the circulationof a heat transfer fluid in the channels and the heat exchange betweenthis heat transfer fluid and the outside through at least one of saidfaces; the network of channels being formed by a three-dimensionalhollow laminated panel (30) based on fibres hardened by the impregnationof a resin, comprising two two-dimensional woven layers which areimpervious and stiff forming said parallel faces (10, 12), and a stiffweaving of orthogonal fibres (14), connecting the two layers together byproviding a hollow intercalated space (16) while forming rows ofparallel walls (20), between them defining the channels (18); means forthe distribution of fluid, arranged between a fluid inlet (42) and oneof the ends of each of the channels of the network; and means for thecollection of fluid, arranged between a fluid outlet (44) and theopposite end of each of the channels of the network; this exchangerbeing characterized in that it does not have attached elements formingmanifolds for the distribution of fluid, and in that the means for thedistribution, respectively the collection, of fluid are meansincorporated into the hollow laminated panel, comprising a longitudinalrecess (38) produced in the laminated panel along a longitudinal edge ofthe latter forming an angle with the direction of the channels, thisrecess (i) opening onto the inner side of the longitudinal edge on saidchannels, (ii) being closed on the outer side of this same edge, and(iii) being in fluidic communication with said inlet, respectively saidoutlet, of fluid.
 2. The heat exchanger of claim 1, in which the recess(38) is defined by a gap blocked out between the longitudinal edge ofthe laminated panel and an outer covering (34) extending over one of thefaces of the laminated panel and opening onto the longitudinal edges ofthe latter.
 3. The heat exchanger of claim 1, in which the recess (38)is formed by removing material in a region of one of the faces of thelaminated panel along the longitudinal edge of the latter, so as todefine a U-section groove directed perpendicularly to the plane of thefaces and opening onto said face.
 4. The heat exchanger of claim 3, inwhich the outlet of the U-section groove is closed by an outer covering(36) of the panel, extending over the face where the recess is formed.5. The heat exchanger of claim 1, in which the recess (38) is defined byremoving material from the sheared edge of the laminated panel along thelongitudinal border of the latter, so as to define a U-section groovedirected parallel to the plane of the faces and opening towards theoutside of the sheared edge.
 6. The heat exchanger of claim 5, in whichthe outlet of the U-section groove is closed by an edging profile (46)arranged along the sheared edge of the laminated panel.
 7. The heatexchanger of claim 1, comprising moreover an insert (48) for guidingfluid and/or creating turbulence, housed in the longitudinal recess(38).
 8. The heat exchanger of claim 1, in which said insert (48) is atwisted tape with a helical configuration.
 9. The heat exchanger ofclaim 1, in which the laminated panel (30) has a non-rectangular shapeof a parallelogram, this panel being arranged vertically with the meansof distribution and collection of fluid inclined with respect to thehorizontal, and with the fluid inlet (42) placed in a low position andthe fluid outlet (44) placed in high position, so as to allow a naturalcirculation of the heat transfer fluid in the exchanger by thethermosiphon effect.
 10. The heat exchanger of claim 1, comprising aplurality of triangular or trapezoid panels assembled in roof panels,these panels being arranged with the channels oriented in a verticalplane, the recesses forming means for the distribution of fluid and thefluid inlet (42) being situated in the lower part of the panel, therecesses forming means for the collection of fluid and the fluid outlet(44) being situated in the upper part of the panel and along the crestsof said roof, so as to allow a natural circulation of the heat transferfluid in the panels by the thermosiphon effect.